vocabulary

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mid-ocean ridge: undersea mountain chain where new ocean floor is produced; a divergent plate boundary
sonar: system that determines the distance of an object under water by recording echo of sound waves; gets its name from sound navigation and ranging
sea-floor spreading: process by which molten material adds new oceanic crust to the ocean floor
deep-ocean trenches: deep valley along the ocean floor through which oceanic crust slowly sinks through mantle
subduction: process by which oceanic crust sinks beneath a deep ocean trench and back into the mantle at an convergent plate boundary

Outline:

Mapping the Mid-Ocean Ridge
East Pacific Rise= one part
Longest chain of mountains
Scientists use sonar for Mid-Ocean Ridge
Evidence for sea-floor spreading:
Continents moving
Movement starting at the mid-ocean ridge
Molten materials erupts after moving out of the mantle
Subduction at Deep-Ocean Trenches:
subduction taking place
Older and denser oceanic crust in the deep-ocean trenches
Oceanic crust is new and hot
Giant conveyor belt= mid-ocean ridge
Subduction and Earth's Oceans:
Atlantic ocean expanding
Pacific ocean decreasing
Why? Ridge not moving fast enoughin adding new crust